In terms of consumption, when you talk about a certain amount of cod, for example, you must not forget that it is part of a food chain. If the overabundance of seals is detrimental to another species, you must bear in mind that that species feeds other species, which feed other species, which feed other species, and so on. Biologists do not always measure that impact.
Biologists have often been criticized for adopting a point of view that is not comprehensive enough. In recent years, they have attempted to adopt a much more ecosystemic approach, in other words, more comprehensive. Clearly, that is not easy to measure. Nevertheless, we must not forget about the effect on the food chain.